212 



HAKDWICKE'S SCIENCE-GOSSIP. 



mains were shown to belong to the Middle Pur- 

 becks, a part of the series not now existing in Port- 

 land. A similar bed, but much thicker, was then 

 described at Chesiltou, in j the north of the island. 

 It is there sixty feet thick, and contains large 

 blocks of Portland stone and Portland chert, the 

 greater number of which are in the upper part of 

 the deposit, v^hich is here on the sea-level, and 400 

 feet lower than the Portland escarpment which rises 

 above it. This loam and angular debris the author 

 was disposed to attribute to a temporary sub- 

 mergence of the land to a depth exceeding the 

 height of Portland, and by which the land as it 

 emerged was swept, and its debris carried down to 

 the lowest levels, with the remains of its land 

 animals and land and fresh-water shells, which 

 latter, where protected by large masses of loam and 

 suddenly entombed, have been preserved uninjured. 

 To this deposit, which is common over the raised 

 beaches on the south coast, the author proposed to 

 apply the term "Laud- wash." The paper con- 

 cluded with a short notice of the drift-beds formed 

 subsequently to the denudation of tlie Weymouth 

 district, and therefore never on the high-level 

 Portland drift. Amongst these was one near Wey- 

 mouth of singular character, consisting almost 

 entirely of subangular fragments of Greensand 

 chert, which could not have been derived from beds 

 nearer than Abbotsbury. The lower drift of the 

 district is the valley-gravel of Upway and Radipole, 

 in which the remains of the Elephas primigenim 

 have been found. 



Basalt. — la reply to some of Mr. H. P. Malet's 

 queries on this subject, iu the June number of 

 Science-Gossip (p. 139), I may refer him to a 

 paper by the late Prof. Fowues "On the Existence 

 of Phosphoric Acid iu Rocks of Igneous Origin." 

 This paper was read before the Royal Society on 

 April 25th, 1844, and published both in the 

 Philosophical Transactions (1844, part i. p. 53) and 

 in the ~Edin. New Phil. Journal (xxxvii. 1844, p. 294). 

 Eownes's researches showed that phosphoric acid 

 exists in the lavas of Vesuvius and in some of the 

 old Rhenish lavas ; not to mention other rocks to 

 which an eruptive origin may fairly be attributed. 

 Moreover, Sullivan detected phosphoric acid in 

 obsidian from the Lipari Isles; C. Sainte-Claire 

 DeviUe found from 1'4 to 2'2 per cent, of phos- 

 phate of lime in the lava erupted from Vesuvius in 

 1855 ; and Kosmann has recorded 058 per cent, of 

 phosphoric acid in the basaltic lava from the Puy 

 de Cohere, in Auvergne. As to basalts, they 

 commonly yield phosphoric acid when carefully 

 examined. "It almost seems," says Zirkel, "as 

 though we should find phosphoric acid in most 

 basalts, if we only sought specially f?r it, or tested 

 a sufficiently large quantity of the rock. And it 

 cannot be doubted that the apatite existing in the 



basalt is the source of this phosphoric acid." 

 ("Basaltgesteine,"lS70,p. 72.) Microscopic crystals 

 of apatite are, indeed, extremely common in 

 basalts, and they also occur in many other rocks to 

 which an igneous origin is commonly attributed. A 

 list of these apatite-bearing rocks will be found in 

 Rosenbusch's "Mikroskopische Physiographic," 

 1873, p. 221. On the disintegration of a rock its phos- 

 phates pass into the soil, whence they are abstracted 

 by growing plants, and thus pass ultimately to the 

 animal organism, where they are concentrated in 

 certain tissues, such as bone. On the decomposi- 

 tion of the animal matter, the phosphates are 

 returned to the soil, and the cycle of changes is 

 thus completed. It is clear, however, that all soils 

 do not derive their phosphates from organic 

 sources ; a sheet of recently-erupted lava, for 

 example, may be extremely fertile, and the plants 

 growing in such a situation must needs obtain 

 their phosphates solely from the mineral con- 

 stituents of the lava. Indeed phosphatic minerals, 

 so far from being absent from rocks of 

 igneous origin, are among their most common 

 constituents. "There can be little doubt," says 

 Fownes, speaking specially of mineral phosphates, 

 " that the matter erupted from time to time from 

 the interior of the earth, in a state of fusion, is thus 

 destined to renew the surface, from which the more 

 valuable and more soluble components have gra- 

 dually been removed by the action of water, and 

 other causes constantly iu operation." With 

 reference to the occurrence of olivine in basalt> 

 little need be said. As Mr. Malet speaks of olivine 

 as "a product of saliciue, whicii is formed of the 

 bark and leaves of trees," it is clear that he is not 

 referring to the olivine of the mineralogist. Un- 

 fortunately Mulder many years ago applied the 

 name of olivine to a resinous substance obtained by 

 the action of certain reagents on saliciue ; yet it 

 need liardly.be said that this rare chemical product, 

 now almost forgotten, does not occur in basalt. 

 The olivine which does occur there is a silicate of 

 magnesia, containing more or less iron. This 

 mineral is not only one of the most common 

 accessory constituents of basalt, but is also found 

 in certain lavas, the igneous origin of which is of 

 course indisputable. It appears, therefore, that 

 the occurrence of apatite and olivine iu basalt can 

 hardly be used as an argument in favour of Mr. 

 Malet's view of the origin of this rock. He has 

 told us, in " The Circle of Light, or Dhawalegeri," 

 that " basalt is a hard, colourless, dark rock, such 

 as would be formed under the water, ere light gave 

 her colours to the world." Mr. Malet, however, 

 does not stand alone even in the present day, in 

 denying the igneous origin of basalt. The Nep- 

 tunian theory is advocated, for example, with 

 much abihty, in Dr. Mohr's " Geschichte der Erde " 

 (Bonn, 1S6G).— F. TF. Rucller. 



